Preparation of mixed chlorohydrides of aluminum

ABSTRACT

Preparation of mixed chlorohydrides of aluminum, especially AlH2Cl, particularly in a solvent system comprising primarily dimethyl ether of ethylene glycol, by a reaction between, for instance, 1 mole of aluminum chloride with 2 to 4 moles of lithium hydride in the presence of an ethylene glycol ether such as diethylene glycol dimethyl ether, and desirably also in the presence of a liquid hydrocarbon such as benzene or toluene. The mixed chlorohydrides of aluminum are useful as reducing agents in various reducing reactions.

United States Patent [1 1 Hoffman et a1.

[ Dec. 16, 1975 PREPARATION OF MIXED CHLOROHYDRIDES OF ALUMINUM [75] Inventors: Doyt K. Hoffman; Ricardo O. Bach,

both of Gastonia, NC.

[73] Assignee: Lithium Corporation of America,

' New York, NY.

[22] Filed: Mar. 21, 1973 [21] Appl. No.: 343,266

[52] US. Cl. 252/188; 423/299; 423/347; 423/472; 423/495 [51] Int. Cl. C01B 6/06; COlF 7/56 [58] Field of Search 252/188, 105; 149/87; 423/472, 495, 644, 645, 111

[56] References Cited UNITED STATES PATENTS 2,468,260 4/1949 Gibb 423/119 2,576,311 11/1951 Schlesinger 252/188 3,076,047 1/1963 Seubold 260/683.15

3,346,506 10/1967 Beumel 252/188 3,355,262 11/1967 Beaird 423/644 3,495,956 2/1970 Roberts... 423/472 X 3,639,104 2/1972 Ashby 423/644 3,812,244 5/1974 Schmidt 423/645 FOREIGN PATENTS OR APPLICATIONS 645,706 1964 Belgium 423/472 823,496 11/1959 United Kingdom .42 3/645 OTHER PUBLICATIONS M. Ferles: Aluminum Hydride and Aluminum Chloride Hydride in Organic Chemistry, Chem. Listy, 62(9), 1968, pp. 1045-1065.

Primary ExaminerDennis E. Talbert, Jr.

Assistant ExaminerDennis L. Albrecht Attorney, Agent, or Firm-Wallenstein, Spangenberg, Hattis & Strampel [57] ABSTRACT Preparation of mixed chlorohydrides of aluminum, especially AlI-l C1, particularly in a solvent system comprising primarily dimethyl ether of ethylene glycol, by a reaction between, for instance, 1 mole of aluminum chloride with 2 to 4 moles of lithium hydride in the presence of an ethylene glycol ether such as diethylene glycol dimethyl ether, and desirably also in 'the presence of a liquid hydrocarbon such as benzene or toluene. The mixed chlorohydrides of aluminum are useful as reducing agents in various reducing reactions.

16 Claims, No Drawings PREPARATION OF MTXED CHLOROHYDRIDES F ALUMINUM Our invention is directed to the novel preparation of highly advantageous mixed chlorohydrides of aluminum, particularly in the form of high-boiling ether, notably, polyethylene glycol alkyl ether, solutions, which can be used effectively as selective hydrogenating and reducing agents, particularly in organic reactions of various types.

It has been well known heretofore to use All-l as a selective hydrogenating and reducing agent in various organic reactions. Various methods for the production of AlH and various uses thereof have heretofore been disclosed. One of such methods involves a two-step procedure, starting with LiH, wherein the latter is initially reacted with AlCl in thepresence of certain ethers, notably, diethyl ether, to produce lithium tetrahydridoaluminate or lithium aluminum hydride (LiAlH and the latter is then reacted with AlCl in the presence of certain ethers, usually diethyl ether. Solutions of AlH in ethers are quite unstable. This is particularly the case where the ether is diethyl ether (DEE). Somewhat more stability occurs where the ether is dimethyl ether (DME) or a cyclic ether such as tetrahydrofuran (THF). The glymes, which are mono-, di-, triand tetraethylene glycol dimethyl ethers, have been found to give very stable solutions.

Another heretofore known procedure for preparing AlH starting with LiAll-I involves reacting the latter with a tertiary amine hydrochloride in the presence of an ether. Such reactions cannot satisfactorily be carried out in liquid hydrocarbon media because of the lack of solubility of the LiAlH in such media. However, tertiary amine complexes (AIH 'NR can be isolated from the reaction of the LiAll-L, with the tertiary amine hydrochloride in the presence of an ether, and said complexes can be dissolved in liquid aromatic hydrocarbons such as benzene.

Certain of the aforesaid procedures for the preparation of AlH and reducing organic reactions in which AlH is used, are shown in Ber. 75, 2003 (1942); J. Am. Chem. Soc. 69, 1199 (1947); J. Am. Chem. Soc. 77, 3164 (1955); German Pat. Nos. 1,024,062; 1,039,041 and 1,141,623;J. Am. Chem. Soc. 88, 1464 (1966) and J. Am. Chem. Soc. 90, 2927 (1968). i

It has also been known that tertiary amines, for instance, trimethylamine (TMA), stabilize All-l in its solutions, the addition of TMA toethereal solutions of NH, leading to the formationof complexes such as All-l .N(CH as indicated above and as obtained by various alternative procedures. J. Am. Chem. Soc. 83, 535 (1961).

It has also heretofore been disclosed, as shown in British Pat. No. 823,496, in connection with the production of high purity silicon from silicon tetrachloride (SiCl to react the SiCl, with an aluminum-containing hydride, such as LiAlH4,:in a medium comprising a dialkyl ether of a polyethylene glycol, such as dimethyl ether of tetraethylene glycol. This reaction results in reducing the SiCL, to SiH which, in turn, is thermally lars per pound of active hydrogen, efforts have been made to find reducing agents which are effective but which provide more economical sources of active hydrogen than the tetrahydridoaluminates. Such efforts have also been directed to overcoming the serious restriction on the utilization of LiAlH, due to the fact that there are only limited types of solvent media in which it may be employed. Thus, as indicated above, nonpolar liquid solvent media such as hydrocarbons, while desirable as media in which to carry out various reducing organic reactions, generally cannot be utilized.

Compounds exemplified by diisobutylaluminum hydride, HAl(C H are soluble in various liquid hydrocarbons and can be used as reducing agents but their cost, in terms of active hydrogen per pound, is quite high.

Sodium bis (2-methoxy ethoxy) dihydridoaluminate, NaAl(OCH CH OCH l-l in the form of solution in benzene (US. Pat. No. 3,507,895) has been suggested for use as a reducing agent for various organic reactions. However, it has a very low active hydrogen content, the price is high and, in addition, its use introduces certain undesirable aspects in certain types of reducing reactions. v

Still another type of compound, exemplified by sodium diethyl dihydridoaluminate, NaAl(C H )H has been offered for-sale in the form of a 25% solution in xylene for use as a reducing agent. As in the case of sodium bis (2-methoxy ethoxy) dihydridoaluminate, the presence of an alkali metal ion has to be taken care of in the workup after the reducing reaction although the cost of the active hydrogen per pound is materially less than in the case of the others of said reducing agents referred to above. Furthermore, the basicity of the hydrolyzed product solutions is a disadvantage where sensitive groupings such as aldehydes or ketones are present in the desired product.

In accordance with our invention, solutions of mixed chlorohydrides of aluminum in liquid solutions can be prepared which exhibit good stability and which provide active hydrogen at a relatively low cost per unit weight.

In the practice of our invention, LiH and AlCl are reacted in a mole ratio in the range of about 1 to 4 of LiH to l of AlCl in a solvent mixture of a liquid hydrocarbon medium, particularly benzene or toluene, and in a dialkyl ether of ethylene glycol or a polyethylene glycol, particularly the dimethyl ether of ethylene glycol (hereafter designated MG). The optimum mole ratio of LiH to AlCl depends, generally, on the particle size of the LiI-L'the amount of dialkyl ether of the ethylene glycol or of the polyethylene glycol employed, and the reaction time. The particle size of the LiH is variable, the finer the size the more rapid, generally, the rate of reaction. A particle size of commercial -35 mesh Lil-I gives a satisfactory conversion rate, but particle sizes of -l00 mesh result in a faster and more complete conversion. The volume ratio of the dialkyl ether of the ethylene glycol or polyethylene glycol to the liquid hydrocarbon in the reaction mixture is variable but, generally, it is desirably from 1 to 4 of said ether to 1 of the liquid hydrocarbon, but, in the broader aspects of our invention, the reaction can be carried out in the absence of the liquid hydrocarbon. Generaly speaking, at the lower ratios of the said ether to the liquid hydrocarbon, the rate and extent of the reaction are decreased. The reactants are utilized, or adjusted during the reaction, so that the final concentration of the All-l cl where x is and up to but not including 3, is advantageously between about 0.1 and 2 moles per liter of solution.

The dialkyl ethers of the ethylene glycol or of the polyethylene glycols which are utilized are those having a basicity such as to enable the replacement of the chlorine in the AlCl or other halogen of the aluminum trihalide used, by hydrogen from the Lil-l, or other alkali metal hydride used, so as to produce AlH Cl or All-lcl as the case may be. Generally speaking, the glycols and polyglycols, of which the dialkyl ethers are utilized, will contain from 2 to 8 carbon atoms; and the alkyl groups of the dialkyl ethers of said glycols and polyglycols will each contain from 1 to 3 carbon atoms. Typical examples of said glycols and polyglycols are ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and dipropylene glycol. The alkyl radicals may be methyl, ethyl, propyl and isopropyl. Examples of the dialkyl ethers are, thus, dimethyl ether of ethylene glycol; dimethyl ether of propylene glycol; dimethyl ethers and diethyl ethers of diethylene glycol, triethylene glycol and tetaethylene glycol; and dipropyl and diisopropyl ethers of the aforementioned glycols and polyglycols.

It may be noted that the dialkyl ethers of the glycols and polyglycols act as Lewis bases to complex with and solubilize AlCl This reaction is very exothermic and, therefore, should be carried out under controlled conditions. One illustrative way of controlling the reaction is to slurry the AlCl in the liquid hydrocarbon and then add the selected dialkyl ether of the ethylene glycol or polyethylene glycol slowly until enough has been added to complex the AlCl This, however, generally produces a waxlike solid which presents certain difficulties in handling due to the insolubility of the complex in the liquid hydrocarbon.

It is particularly desirable, therefore, to effect a control of the reaction in the following manner. Since the dimethyl ether (DME) complex of AlCl is soluble in aromatic hydrocarbons and is readily formed by purging DME into a stirred AlCl -liquid hydrocarbon slurry, the resulting solution is then used to prepare a solution of the dialkyl ether of the ethylene glycol or polyethylene glycol or to carry out the reaction directly in said dialkyl ether. Since said dialkyl ethers are stronger Lewis bases and have boiling points much higher than that of DME, the DME will be expelled from the dialkyl ether solutions at room temperatures.

Another manner in which to effect a control of the reaction is to prepare, as a first step in the reaction, a mixed salt composed of AlCl and either LiCl or NaCl. These salt combinations can be prepared by melting the 1:1 mole mixture together at about 100C. After cooling, this material can then advantageously be dissolved in the selected dialkyl ether of the ethylene glycol or polyethylene glycol for the preparation of the mixed chlorohydride.

The reaction between the LiH and the AlCl which generally results in the production of chlorodihydroaluminate, is carried out by suspending the LiH in a flask containing the dialkyl ether of ethylene glycol or polyethylene glycol, in an inert atmosphere, by slowly adding the AlCl solution. The heat of the reaction is removed either by ambient air or by a cooling bath. Generally, where the dialkyl ether is MG, the reaction proceeds to the replacement of 2 atoms of chlorine whereby to produce AlH Cl, even when a 1 mole excess of LiH is used in one stage, i.e., 3 LiH to l AlCl 4 By-product LiCl remains in solution up to about 1 molar (Li: A1 2). Above this ratio, unsolvated LiCl precipitates.

When dimethyl ethers of di-, tri-, or tetraethylene glycol are used instead of the dimethyl ether of ethylene glycol, the conversion of the AlCl is generally to All-lCl The addition of fresh LiH in small increments does not result in carrying the conversion to, or approaching, All-l However, where the dimethyl ether of ethylene glycol is used, the addition of fresh LiH in small increments pushes the reaction to, or approaching, the production of All-I In the practice of the invention, it is particularly advantageous to utilize, as an initiator in the reaction between the Lil-l and the AlCl a small amount of proportion of preformed AlH or an alkali metal tetrahydridoaluminate such as LiAlI-I or NaAlH Small proportions of such initiators, when employed, are utilized, generally of the order of about 0.5 to 5% by weight of the Lil-l used in the reaction.

While, as pointed out above, benzene or toluene, or mixtures thereof, are especially satisfactory liquid hydrocarbons for use as the hydrocarbon reaction medium, other liquid hydrocarbons can be used illustrative examples of which are cyclohexane, isooctane, o-, mand p-xylenes and mixtures of two or more of them, methylbenzene, isopropylbenzene, diethylbenzene and the like. Generally, liquid aromatic hydrocarbons are particularly preferred.

It is particularly desirable to utilize LiH as the starting alkali metal hydride. However, it is also within the scope of our invention to use other alkali metal hydrides as, for example, Nal-I, KH, CsH and RbH. Similarly, where alkali metal tetrahydridoaluminates are used as initiators, the alkali metal can be, in addition to Li or Na, K, Cs and Rb.

While AlCl is most advantageously used in the reaction with the alkali metal hydride to produce the mixed chlorohydrides of aluminum in accordance with the present invention, A1Br as well as A11 can be used in place thereof.

The following examples are illustrative of the practice of our present invention. It will be understood that procedural variations may be made in the light of the guiding principles and teachings disclosed herein. All temperatures recited are in degrees C.

EXAMPLE 1 A l-liter, 3-neck, round-bottom flask is fitted with a 250 m1 dropping funnel, an argon purge inlet with thermometer, a water condenser attached to an oil bubbler, and a magnetic stirrer. After thoroughly purging the apparatus, 12 g of lOO mesh Lil-l 1.5 moles) and 500 ml of distilled MG are placed in the flask together with 0.3 g of preformed LiAlH as an initiator. Then an AlCl solution, prepared from a slurry of 66 g AlCl (0.5 moles) in ml of distilled toluene by slowly purging -25 g DME (-0.5 moles) thereinto, is slowly dripped into the stirred slurry of the LiH in the MG in the flask over about 1 hour. The rate of addition is such as to maintain the temperature in the range of 405 0. The DME escapes as the AlCl solution comes into contact with the MG. The reaction mixture is stirred for an additional 2.5 hours after the addition of the AlCl solution is completed. The reaction mixture is then filtered, and an aliquot of the solution is hydrolyzed and the evolved hydrogen measured. The conversion is about 92% as AlH Cl based on the AlCl used, or

61% based on the Lil-I used. It may be noted that the unreacted LiH is not lost and, if desired. it canbe recycled for further use.

EXAMPLE 2 Example 1 is repeated with the following modification: the order of addition is reversed so that the Lil-I is added incrementally to the AlCl solution in MG. The conversion is 95% to AlI-I Cl based on AlCl and 65% based on Lil-I.

' EXAMPLE 3 Example 1 is repeated but using 14.3 g 35 mesh LiH (18 moles), and the reactants are stirred for about 6 hours and then filtered. The conversion is about 94% to AlH Cl based on AlCl,-,.

EXAMPLE 4 EXAMPLE 5 The filtered solution from Example 1 is treated with 6 g of 100 mesh LiI-I for 12 hours. The resulting solution contains A], Hand Cl (bound to Al) in the following ratio: l:2.6:0.4. This shows that the replacement of the third chlorine on aluminum is much more difficult than the first and second step with MG solvent.

EXAMPLE 6 Example '1 is repeated except that diethylene glycol dimethyl ether (DG) is used in place of MG. The conversion is 100% to AlHCl based on AlCl EXAMPLE 7 EXAMPLE 1 is repeated except that tetraethylene glycol dimethyl ether (TG) is used in place of MG. The conversion is 98% to All-[C1 based on AlCl A sample of the above solution is treated with an amount of LiH which, stoichiometrically, would be sufficient to react with the remaining chloride and to convert it to All-I Stirring for 16 hours does not significantly increase the hydride content above AlI-ICl EXAMPLE 8 24 g of NaH (lmoIe) are reacted with a mixture consisting of 29 g NaCl (0.5 mole) and 66 g AlCl (0.5 mole) contained in 300 ml of MG, under the conditions described in Example 1, to produce 23 g of AlH Cl (0.36 moles) in'300 ml of solution containing excess NaCl for a conversion of 72%.

EXAMPLE 9 Example 8 is repeated but using 8 g Lil-l (1 mole) and 21 giLiCl (0.5 mole) plus 66 g AlCl (0.5 mole) to produce 32 g of AlH Cl (0.5 mole).

Mixed aluminum chlorohydride solutions made in accordance with our present inventionhave highly effective utility in various organic reactions, notably as reducing agents. In certain cases, inorganic reactions are substantially quantitative without the formation of 6 undesirable byproducts. For instance, SiCl, is transformed essentially quantitatively to SiH and PCl is converted to PH in, generally 30 to 50% conversion in accordance with the following equations, respectively:

1. SiCL; ZAIH CI SiI-I, 2AlCl 2. SiCl 4AlHCl SiI-L, 4AlCl 3. 2PCl 3AlI'I Cl 2PH 3AlCl 4. PCl 3AlHCl PH 3AlC1 Silicon chlorohydrides can also effectively be produced using the chlorohydrides made in accordance with our invention.

Illustrative examples of the uses of the mixed chlorohydrides of aluminum of our invention are set forth below.

n EXAMPLE 10 Preparation of SiI-I by Reduction of SiCl with AlH Cl A 250 ml, 3neck flask is fitted with an argon inlet tube, a 250-ml dropping funnel and a dry-ice condenser and outlet connection. Into the flask is placed ml of a MG solution containing 20 millimoles of A1H Cl. Through the dropping funnel, 8 millimoles of SiCL, are slowly admitted to the flask at room temperature and with constant stirring provided by a magnetic stirrer and stirring bar. The evolved gas is allowed to pass from the reaction through the condenser and into a tared section of Vycor tubing; the tubing is packed with glass wool on each end and heated to a dull-red glow. The deposited silicon, determined by weight difference, 210 mg, for a yield of crude silane of 94% based on SiCl used.

In addition, the above solution, now containing essentially AlCl is treated with 0.32 g of Lil-I by stirring together for 2 hours and then filtering. The resulting solution contains about 20 millimoles of AlI-I Cl.

As the above reaction is carried out, the active hydrogen species in solution passes from AlH Cl through AlHCl and eventually would have gone to AlCl had sufficient SiCl been added. Hence, it is apparent that either form of the mixed chloraluminum hydride may be used to prepare SiI-I under these conditions and in excellent yield as long as the appropriate stoichiometries are observed.

EXAMPLE 11 Preparation of SiH C1 Dichlorosilane may be prepared by a generally similar method to the above example. However, since SiH, is formed so rapidly and completely, the reaction must be carried out so that a deficiency of active hydrogen reducing agent is present in the reaction. (Hence, an inverse addition method is used.) In addition, cooling to low temperatures, e.g., about 0C, is advantageous.

l0 millimoles of SiCl is placed in a flask and 100 ml of an MG solution containing 20 millimoles of All-1 C] is placed in the dropping funnel. The flask is cooled to 0. The MG solution is then added slowly with stirring and any evolved gas is collected and decomposed in a gas impinger containing alcoholic KOI-I. After stirring for 30 minutes, a fresh impinger and solution of alcoholic KOH is used to catch the fraction of gas evolved when the dry-ice condenser is replaced by a watercooled condenser and the reaction mixture heated to 35.

The two fractions of product collected in the impingers are analyzed for silicon and chloride to determine the composition of gaseous products. In the first frac- 7 tion, SiH, accounts for about 70% of the total silicon collected, while, in the second fraction, SiH Cl is the empirical composition accounting for the remaining 30%.

While, as indicated above, the halohydrides of aluminum will generally correspond to the formulae AlH Cl and AlHCl the contents of halogen and hydrogen can vary, the atoms of halogen and hydrogen per simplified molecule adding up to 3, illustrative examples of such halohydrides of aluminum being exemplified by formulae such as All-1 C1 All-I Cl, etc. Thus, said halohydrides of aluminum can be represented by the formula AlH,,Cl,,, where hydrogen and chlorine are present in the molecule and where the sum of n and m is 3.

We claim:

1. In a method of preparing liquid solutions of aluminum compounds corresponding to the formula AlH, Hal where x is O and up to but not including 3, the steps which comprise reacting an alkali metal hydride with All-lal where Hal is halogen selected from the group consisting of chlorine, bromine and iodine, in a mole ratio of about 1 to 4 moles of said alkali metal hydride to 1 mole of said AlHal in a liquid medium comprising a dialkyl ether of a glycol selected from the group consisting of ethylene glycol, propylene glycol and their polyglycols, said glycol containing from 2 to 8 carbon atoms, the alkyls of said dialkyl radical containing from 1 to 3 carbon atoms, whereby to produce a final concentration between about 0.1 and 2 moles of the All-l,.l-lal per liter in said solutions.

2. The method of claim 1, in which the liquid medium also includes a liquid aromatic hydrocarbon, the volume ratio of said dialkyl ether to said hydrocarbon being from l to 4 of said dialkyl ether to 1 of said hydrocarbon. l i

3. The method of claim 2, in which the alkali metal hydride is lithium hydride, and Hal is chlorine.

4. The method of claim 3, in which the liquid hydrocarbon is at least one member selected from the group consisting of benzene and toluene.

5. The method of claim 4, in which there is included in the reaction mixture an initiator in the form of at least one member selected from the group consisting of a preformed All-l and an alkali metal tetrahydridoaluminate, said initiator being utilized in amounts of about 0.5 to 5% by weight of the lithium hydride.

6. The method of claim 1, in which the alkyl groups of said dialkyl ether are methyl.

7. The method of claim 4, in which the alkyl groups of said dialkyl ether are methyl.

8. In a method of preparing liquid aromatic hydrocarbon solutions of mixed chlorohydrides of aluminum, the steps which comprise:

a. providing a slurry of LiH in a dialkyl ether of a member selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol and in which each alkyl contains from 1 to 2 carbon atoms,

b. providing a solution of AlCl in at least one liquid aromatic hydrocarbon selected from the group consisting of benzene and toluene, said solution also containing dimethyl ether, the volume ratio of said dialkyl ether to said hydrocarbon being from 1 to 4 of said dialkyl ether to l of said hydrocarbon,

c. the ingredients being proportioned so that the mole ratio of Lil-l to AlCl in the (a) and (b) compositions is about 1 to 4 of Lil-l to 1 of AlCl and d. gradually adding the (b) solution to the (a) slurry, whereby to produce a final concentration between about O.l and 2 moles per liter of the mixed chlorohydrides of aluminum in said solutions.

9. In a method of preparing liquid solutions of mixed chlorohydrides of aluminum, the steps which comprise:

a. providing a slurry of Lil-l in a dialkyl ether of a member selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol and in which each alkyl contains from 1 to 2 carbon atoms,

b. providing a solution of AlCl and NaCl or LiCl in a substantially 1:1 molar ratio in a dialkyl ether of a glycol selected from the group consisting of ethylene glycol, propylene glycol and their polyglycols, said glycol containing from 2 to 8 carbon atoms, the alkyls of said dialkyl radical containing from 1 to 3 carbon atoms,

c. The ingredients being proportioned so that the mole ratio of LiH to AlCl in the (a) and (b) compositions is about 1 to 4 of LiH to l of AlCl and d. gradually adding the (b) solution to the (a) slurry,

whereby to produce a final concentration between about 0.1 and 2 moles per liter of the mixed chlorohydrides of aluminum in said solutions.

10. The method of claim 8, in which said (a) slurry also contains an initiator in the form of at least one member selected from the group consisting of a preformed AlH and an alkali metal tetrahydridoaluminate, said initiator being utilized in amounts of about 0.5 to 5% by weight of the Lil-I.

11. The method of claim 8, in which during step (d) at least a part of the dimethyl ether is allowed to evaporate from the reaction mixture.

12. The method of claim 9, in which said (a) slurry also contains an initiator in the form of at least one member selected from the graup consisting of a preformed All-I and an alkali metal tetrahydridoaluminate, said initiator being utilized in amounts of about 0.5 to 5% by weight of the UH.

13. The method of claim 6, in which the alkyl groups of said dialkyl ether are methyl.

14. A solution of a halohydride of aluminum in a liquid aromatic hydrocarbon solvent and a dialkyl ether of a glycol selected from the group consisting of ethylene glycol, propylene glycol and their polyglycols, said glycol containing from 2 to 8 carbon atoms, the alkyls of said dialkyl radical containing from 1 to 3 carbon atoms, said solution containing from about 0.1 to 2 moles of said halohydride of aluminum per liter, said halohydride corresponding to the formula Alll,,Cl,, where the sum of n and m is 3, and also halo of said halohydride being selected from the group consisting of chlorine, bromine, and iodine.

15. A solution according to claim 14, in which the alkyl groups of said dialkyl ether are methyl groups.

16. A solution according to claim 15, in which the aromatic hydrocarbon solvent is a member selected from the group consisting of benzene and toluene. 

1. IN A METHOD OF PREPARING LIQUID SOLUTIONS OF ALUMINUM COMPOUNDS CORRESPONDING TO THE FORMULA AIHXHAL3-X WHERE X IS 0 AND UP TO BUT NOT INCLUDING 3, THE STEPS WHICH COMPRISE REACTING AN ALKALI METAL HYDRIDE WITH ALHAL3, WHERE HAL IS HALOGEN SELECTED FROM THE GROUP CONSISTING OF CHLORINE, BROMINE AND IODINE, IN A MOLE RATIO OF ABOUT 1 TO 4 MOLES OF SAID ALKALI METAL HYDRIDE TO 1 MOLE OF SAID AIHAL3, IN A LIQUID MEDIUM COMPRISING A DIALKYL ETHER OF A GLYCOL SELECTED FROM THE GROUP CONSISTING OF ETHYLENE GLYCOL, PROPYLENE GLYCOL AND THEIR POLYGLYCOLS, SAID GLYCOL CONTAINING FROM 2 TO 8 CARBON ATOMS, THE ALKYLS OF SAID DIALKYL RADICAL CONTAINING FROM 1 TO 3 ATOMS, WHEREBY TO PRODUCE A FINAL CONCENTRATION BETWEEN ABOUT 0.1 AND 2 MOLES OF THE AIHXHAL3-X PER LITER IN SAID SOLUTIONS.
 2. The method of claim 1, in which the liquid medium also includes a liquid aromatic hydrocarbon, the volume ratio of said dialkyl ether to said hydrocarbon being from 1 to 4 of said dialkyl ether to 1 of said hydrocarbon.
 3. The method of claim 2, in which the alkali metal hydride is lithium hydride, and Hal is chlorine.
 4. The method of claim 3, in which the liquid hydrocarbon is at least one member selected from the group consisting of benzene and toluene.
 5. The method of claim 4, in which there is included in the reaction mixture an initiator in the form of at least one member selected from the group consisting of a preformed AlH3 and an alkali metal tetrahydridoaluminate, said initiator being utilized in amounts of about 0.5 to 5% by weight of the lithium hydride.
 6. The method of claim 1, in which the alkyl groups of said dialkyl ether are methyl.
 7. The method of claim 4, in which the alkyl groups of said dialkyl ether are methyl.
 8. IN A METHOD OF PREPARING LIQUID AROMATIC HYDROCARBON SOLUTIONS OF MIXED CHLOROHYDRIDES OF ALUMINUM, THE STEPS WHICH COMPRISES: A. PROVIDING A SLURRY OF LIH IN A DIALKYL ETHER OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF ETHYLENT GLYCOL, DIETHYLENE GLYCOL, TRIETHYLENE GLYCOL AND TETRAETHYLENE GLYCOL AND IN WHICH EACH ALKYL CONTAINS FROM 1 TO 2 CARBON ATOMS, B. PROVIDING A SOLUTION OF AICI3 IN AT LEAST ONE LIQUID AROMATIC HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF BENZENE AND TOLUENE, SAID SOLUTION ALSO CONTAINING DIMETHYL ETHER, THE VOLUME RATIO OF SAID DIALKYL ETHER TO SAID HYDROCARBON BEING FROM 1 TO 4 OF SAID DIALKYL ETHER TO 1 OF SAID HYDROCARBON, C. THE INGREDIENTS BEING PROPORTIONED SO THAT THE MOLE TATIO OF LIH TO SICI3 IN THE (A) AND (B) COMPOSITION IS ABOUT 1 TO 4 OF LIH TO 1 OF AICI3, AND D. GRADUALLY ADDING THE (B) SOLUTION TO THE (A) SLURRY, WHEREBY TO PRODUCE A FINAL CONCENTRATION BETWEEN ABOUT 0.1 AND 2 MOLES PER LITER OF THE MIXED CHLOROHYDRIDES OF ALUMINUM IN SAID SOLUTIONS.
 9. In a method of preparing liquid solutions of mixed chlorohydrides of aluminum, the steps which comprise: a. providing a sLurry of LiH in a dialkyl ether of a member selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol and in which each alkyl contains from 1 to 2 carbon atoms, b. providing a solution of AlCl3 and NaCl or LiCl in a substantially 1:1 molar ratio in a dialkyl ether of a glycol selected from the group consisting of ethylene glycol, propylene glycol and their polyglycols, said glycol containing from 2 to 8 carbon atoms, the alkyls of said dialkyl radical containing from 1 to 3 carbon atoms, c. The ingredients being proportioned so that the mole ratio of LiH to AlCl3 in the (a) and (b) compositions is about 1 to 4 of LiH to 1 of AlCl3, and d. gradually adding the (b) solution to the (a) slurry, whereby to produce a final concentration between about 0.1 and 2 moles per liter of the mixed chlorohydrides of aluminum in said solutions.
 10. The method of claim 8, in which said (a) slurry also contains an initiator in the form of at least one member selected from the group consisting of a preformed AlH3 and an alkali metal tetrahydridoaluminate, said initiator being utilized in amounts of about 0.5 to 5% by weight of the LiH.
 11. The method of claim 8, in which during step (d) at least a part of the dimethyl ether is allowed to evaporate from the reaction mixture.
 12. The method of claim 9, in which said (a) slurry also contains an initiator in the form of at least one member selected from the group consisting of a preformed AlH3 and an alkali metal tetrahydridoaluminate, said initiator being utilized in amounts of about 0.5 to 5% by weight of the LiH.
 13. The method of claim 6, in which the alkyl groups of said dialkyl ether are methyl.
 14. A solution of a halohydride of aluminum in a liquid aromatic hydrocarbon solvent and a dialkyl ether of a glycol selected from the group consisting of ethylene glycol, propylene glycol and their polyglycols, said glycol containing from 2 to 8 carbon atoms, the alkyls of said dialkyl radical containing from 1 to 3 carbon atoms, said solution containing from about 0.1 to 2 moles of said halohydride of aluminum per liter, said halohydride corresponding to the formula AlHnClm where the sum of n and m is 3, and also halo of said halohydride being selected from the group consisting of chlorine, bromine, and iodine.
 15. A solution according to claim 14, in which the alkyl groups of said dialkyl ether are methyl groups.
 16. A solution according to claim 15, in which the aromatic hydrocarbon solvent is a member selected from the group consisting of benzene and toluene. 